Basically, he should have said least predictable. His point is that Hun wars almost always come down to cavalry archer wars in the castle age, meaning you know what to expect right away. Mayans will do archers or drush followed by FC and plumed archers. Aztecs will do 5-militia drush followed by archers, then crossbows.
What civilization is the HARDEST to predict?
What civilization is the HARDEST to predict?